Shell-based if statement

In determining the size of a value in addition to (()) can be used in the form of [] but can not use;, <, = such a symbol, to use-LT (less than),-GT (greater than),-le (less than equals),-ge (greater than or equal),-eq (equals),-ne (not equal) 。

If statement

if Judgment statement; Then

Command

Fi

If,else statements

if Judgment statement; Then

Command

Else

Command

Fi

If Elif statement

If Judgment statement one; Then

Command

Elif Judgment Statement two; Then

Command

Else

Command

Fi

Three examples:

[email protected] ~]# cat if1.sh

#/bin/bash

Read-p "Input your Source:" A

If [$a-lt];then

echo "You did notpass the exam"

elif [$a-ge]&&[$a-le 85]; Then

echo "You pass the exam"

Else

echo "Your source is very high"

Fi

If statement can determine file attributes and permissions

-E: Determine if a file or directory exists

-D: Determine if the directory is not present and whether it exists

-F: Determine if the file is normal and exists

-R: Determine if the document has Read permissions

-W: Determine if Write permission is available

-X: Determine if executable

-Z: To determine if the variable is empty if [-Z $a] is empty is true.

When you use the If judgment, the specific format is:

If [-e filename]; Then

Example:

[Email protected] ~]# if [-d/home/]; then echo OK; Fi

Ok

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Shell-based if statement